If the ads are to be believed, “Tammy” is the movie that finally wears out Melissa McCarthy’s welcome — another low denominator “Identity Thief,” only this time as a garish vanity project with jokes where she dances and that’s the joke. As it happens, the ads are misleading crap. Here are some ways it’s better than it looks:

Melissa McCarthy is still funny

The key to McCarthy’s gifts isn’t that she’s willing to make an ass out of herself. It’s that her characters tend to have a brash, arrogant confidence in traits few would find admirable. Her breakthrough “Bridesmaids” character is downright hallucinatory in her eccentricities. “Tammy”’s Tammy is more straightforward: She’s a bad luck magnet, but she always soldiers on, even when, as in the film’s opening, she’s fired and learns she’s been cheated on — and this is after hitting a deer with her car. She doesn’t, like the similarly beset-upon Jenny Slate in “Obvious Child,” proceed to get knocked up and schedule an abortion on Valentine’s Day. Instead she runs off on a road trip with her grandma (Susan Sarandon).

Susan Sarandon has a great time as Melissa McCarthy's grandmother (!!) in "Tammy."

It gives her a good sidekick

So far McCarthy has played either second fiddle or co-lead. Here, she’s the centerpiece, and next to her is Susan Sarandon, who’s given gray hair but no other visible aging makeup to pass as her alkie, loose cannon grandmother. (In real life, Sarandon only has 24 years on the woman playing her grand-daughter.) Perhaps because she’s still fairly young, Sarandon isn’t doing Alan Arkin in “Little Miss Sunshine.” She’s alert and flirty, and still enough of a fox that it’s not far-fetched when she gets some tail. Sarandon doesn’t tend to have fun in movies, yet her devil-may-care turn here gives "Tammy" an alert, unpredictable energy, even one that hints at something darker than even Sarandon is willing to dig into. (McCarthy is also joined by a steady procession of capable supporting stars, including Kathy Bates, Allison Janney Gary Cole and a solid Dan Aykroyd, plus a surreally wasted Toni Collette.)

Melissa McCarthy wants you to like her in "Tammy."Credit: Michael Tackett

It has a strange, unwieldy tone

Actually, most of it is pretty much what you expect, given that the producers are Adam McKay and Will Ferrell. It’s a comedy that goes primarily for laughs that are primarily about McCarthy trying to play it cool even as she’s, say, driving with her head out the window due to a busted windshield. (There’s a terrific slow-burn robbery that gets funnier the more it drags things out.) It has a superficially “indie” sheen, which is to say it’s a little rough around the edges, especially considering it’s the probable winner of this July 4’s new releases. (It can’t even stage two accidents without clumsy editing badly obscuring the fact they didn’t actually shoot said accidents.)

Every now and then it goes to weirder, even sadder places. Tammy actually breaks down a time or two. Even when things get emotional, it always quickly retreats to safer (which is to say comedic) places; at one point Tammy is wronged by someone then begs that they skip the apologies and go straight to acting like nothing happened. But the sporadic almost-seriousness gives it a bizarre feeling that’s more likeable than had it actually been committed to being po-faced.

Mark Duplass and Melissa McCarthy get down in "Tammy."Credit: Michael Tackett

It takes McCarthy…almost seriously as a romantic lead

This is a film directed by Ben Falcone, who in real life is married to McCarthy, and the two wrote the script together. It understands that perhaps audiences don’t want to think of McCarthy as having a sex life. It even makes jokes to the effect that she thinks she has a pull over men. (It's not great that Sarandon's grandma is more sexualized then McCarthy's Tammy, though.) And yet she gets a hesitant romance with no less than Mark Duplass, playing an overly mild-mannered handsome shlub first coerced into spending time with her, then finding himself remarking on her beauty — an act done neither as a joke nor as a comment on men finding women of her size sexy, as in a recent episode of “Louie.” In her very first mostly solo vehicle, McCarthy gets to kiss a good-looking actor, and it’s portrayed as completely normal. That might be the most refreshing thing at the movies all summer.